Rheology modifiers are used in waterborne coatings formulations to control viscosity over a wide shear rate range. They may be associative (they associate with the dispersed phase) or non-associative (they thicken the water phase). Associative thickeners may be derived from natural products such as hydrophobically modified cellulose ethers, or prepared from synthetic polymers such as hydrophobically modified ethylene oxide urethane (HEUR) polymers. A typical description of HEUR polymers and their preparation can be found in US 2009/0318595 A1, which describes forming a combination of linear and branched HEUR polymers by reacting a polyglycol, a hydrophobic alcohol, a diisocyanate, and a triisocyanate together in a one-pot reaction. U.S. Pat. No. 4,155,892 (Emmons et al.) describes the preparation of linear as well as branched HEUR polymers in separate examples.